15kHz vs 20kHz vs 35kHz Ultrasonic Welding Machines: How to Choose the Right Frequency

Brief

Choosing the right ultrasonic welding frequency is critical for achieving stable welding quality and

 avoiding common defects such as weak welds, flashing, or material damage.

The most commonly used frequencies are 15kHz, 20kHz, and 35kHz. Each has different characteristics, 

applications, and advantages.

In this guide, we compare these three frequencies and help you select the best ultrasonic welding solution

for your needs.

What Does Ultrasonic Welding Frequency Mean?

Ultrasonic welding frequency refers to the number of vibration cycles per second generated 

by the ultrasonic system.

• Lower frequency → higher amplitude → stronger energy

• Higher frequency → lower amplitude → higher precision

This directly affects weld strength, accuracy, and material behavior.

15kHz Ultrasonic Welding (High Power for Large Parts)

Features

• High amplitude

• Strong welding energy

• Suitable for thick materials

Applications

• Automotive components

• Large plastic parts

• Heavy-duty welding

Advantages

• Strong weld strength

• Suitable for high-load applications

Limitations

• Lower precision

• May damage small or delicate parts

If your application requires stronger weld strength or larger part sizes, consider using a 15kHz system. 

15kHz 4200W ultrasonic plastic welding machine offers stable high-power output for demanding 

industrial environments.

20kHz Ultrasonic Welding (General-Purpose Solution)

Features

• Balanced amplitude and precision

• Widely used frequency

Applications

• Electronics

• Consumer products

• Packaging

Advantages

• Versatile

• Suitable for most applications

Limitations

• Not ideal for extremely large or ultra-precision parts

Recommend 20 kHz machine welding system: 20Khz 3000W ultrasonic welder 

35kHz Ultrasonic Welding (Precision Welding)

 Features

• Low amplitude

• High precision

• Stable welding control

Applications

• Medical devices

• Electronics components

• Small plastic parts

Advantages

• Excellent for delicate products

• Minimal material deformation

Limitations

• Lower power compared to 15kHz

Recommend 35kHz machine welding system: 35Khz 800W Ultrasonic Welding System

How to Choose the Right Ultrasonic Welding Frequency

When selecting the correct frequency, consider:

1. Part Size

• Large parts → 15kHz

• Medium parts → 20kHz

• Small parts → 35kHz

2. Material Type

• Hard plastics → lower frequency

• Delicate materials → higher frequency

3. Welding Precision

• High precision → 35kHz

• General welding → 20kHz

4. Production Requirements

• High output → automation + correct frequency

Choosing the wrong frequency often leads to welding defects such as cracks, flashing, or weak joints.

See ultrasonic Welding Troubleshooting Guide: Common Problems and Solutions

Common Problems Caused by Wrong Frequency

• Weak weld strength

• Excessive flashing

• Material damage

• Inconsistent welding

These issues can often be solved by selecting the correct frequency and optimizing parameters.

When to Use Custom Ultrasonic Welding Solutions

For complex or high-volume production, standard machines may not meet requirements.

Custom automation solutions can provide:

• Multi-station welding

• Automatic feeding

• Vision inspection

• Stable and repeatable quality

FAQ

Q1: Which ultrasonic frequency is best?

A1: There is no single “best” frequency. It depends on part size, material, and precision requirements.

Q2: Can 20kHz replace 35kHz?

A2: Not always. 35kHz is better for precision and delicate parts.

Q3: Why does wrong frequency cause defects?

A3: Incorrect frequency leads to improper energy transfer, causing poor weld quality.

Q4: Is higher frequency always better?

A4: No. Higher frequency means lower power and is not suitable for large parts.

Not sure which ultrasonic welding frequency is right for your product?

TIMEAST provides:

• Machine selection support

• Sample testing

• Custom automation solutions

• Request a Quote →

•  Send Your Samples for Evaluation →